1. Field of the Invention
The present invention relates to a carbon film coated member excellent in low-friction property, wear resistance and durability, and capable of suppressing a dust generation, peeling-off and deterioration of the coated film even if the carbon film coated member is used as semiconductor equipment members such as wafer cassette, dummy wafer, probe pin or the like under severe operating conditions, so that the carbon film coated member would not exert a bad influence onto the resultant semiconductor products.
2. Description of the Related Art
Conventionally, there have been widely used various members over many technical fields. Example of the members may include: a metal member of which surface property is improved by surface modification methods such as gas nitriding methods, ion nitriding, arc-ion plating (AIP) method or the like, thereby to reduce wear of the member; and an iron/steel member of which surface layer is hardened by surface hardening treatments such as carbonizing and quenching method, nitriding method, induction hardening method, flame hardening method or the like, thereby to improve wear resistance property of the member.
On the other hand, in recent years, there has become also widely used a member in which a coating film composed of amorphous carbon is integrally formed onto a surface of a metal base material, the amorphous carbon having a high hardness and a low friction coefficient that are similar to those of diamond.
For example, Japanese Patent Application (Laid-Open. 1997) No. 5-279854 discloses a method of forming this type of the diamond film. Concretely to say, the forming method adopts a process comprising the steps of: ionizing and depositing carbon compound onto a surface of the base material thereby to form a diamond-like carbon film having a predetermined pattern; and thereafter, integrally forming diamond film having a predetermined thickness through a vapor phase synthesizing method.
According to the above forming method, a tight-adhesion property between the surface of the base material and the diamond film is enhanced, and the diamond film can be formed densely and flatly. When a tool body is coated with the above diamond film, the diamond film can be firmly adhered to the surface of the tool body, whereby a wear resistance of the tool can be improved.
On the other hand, as information technology devices represented by a computer or a mobile device have been progressed, an integration degree of a semiconductor integrated circuit to become a main component of the above devices has increased, so that it has been strongly demanded for the integrated circuit to realize a high-speed processing and downsizing of the integrated circuit.
The semiconductor device deeply dislikes an impurity to be mixed into not only starting raw material but also semi-finished products in view of securing good performances, so that each of processes for manufacturing the semiconductor device is normally performed in an environment of which atmosphere is highly cleaned-up and decontaminated as like in a clean-room. It goes without saying that it has been required for also the respective members constituting these semiconductor manufacturing devices so as not to generate any impurity components.
Further, a wafer processing step in semiconductor manufacturing process which is typically represented by dry etching, CVD sputtering and CVD, is performed in a reaction vessel, so-called, chamber of which atmosphere can be decompressed to realize a high vacuum. In general, as a material for constituting this chamber, metal members composed of aluminum or the like have been widely used in view of its high design-freedom and excellence in structural strength.
Conventionally, the metal impurity generated from an inner wall of the chamber has not raised any problems at all. However, in these days, as the integration degree of the semiconductor integrated circuit has drastically increased, it has been required to satisfy a purity standard prescribed with a higher purity level, so that material property with less impurity contamination has been required for the chamber.
As one example of the materials having less impurity contamination, graphite material has been well known. However, a general graphite material is porous in an entire structure, so that it is difficult to attain a high vacuum in the chamber. In addition, fine particles are liable to be generated due to dropping-off of fine grains constituting the graphite structure. There are some cases where the particles may contaminate the integrated circuit thereby to cause defects such as short-circuit or open-defect in the integrated circuits.
On the other hand, as a uniform carbon material having a gas-impermeability, a glassy carbon has been widely used in recent years as a member for constituting the semiconductor manufacturing devices. This glassy carbon has characteristics of that impurity contamination is extremely few and the particle generation is also small due to the uniform and continuous crystalline structure of the glassy carbon.
Further, there exist a dummy wafer as one concrete example of the member for constituting the semiconductor-manufacturing device. This dummy wafer is used as an alternate material to be substituted for a silicon wafer for the purpose of conducting an operation test of jig and machines, and for the purpose of cleaning the process line in LSI and/or VLSI manufacturing process.
In the process for manufacturing the semiconductors such as LSI and/or VLSI, a process for forming a film in accordance with chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sputtering method or the like occupy an important position. The resultant thin film is required to provide a high uniformity. Therefore, a quality control in the film forming process and an evaluation of the thin film are indispensable elements for the semiconductor manufacturing process.
The dummy wafer is used for the quality control in the film forming process and an evaluation of a thin film. Concretely to say, the dummy wafer is used for grasping a relation between the film forming conditions such as film-forming time, wafer temperature or the like and a thickness of the film formed on the wafer, and is also used for conducting a purity analysis of the resultant film. Further, the dummy wafer is also used as a wafer for dummy sputtering operation for the purpose of preventing the particle generation due to falling-off of the film from constituent parts of a sputtering apparatus.
As previously mentioned, the step of forming a film onto the wafer in the semiconductor manufacturing process, which is typically represented by the sputtering method, CVD method, dry etching method and ion-injecting method, is performed in the reaction vessel, i.e., the chamber of which atmosphere can be decompressed to realize a high vacuum. In general, as a dummy wafer to be used for this film-forming device, a single crystal silicon wafer has been adopted because the contamination by impurity is few and the particle-generation resulting in lowering a production yield is also small. In this connection, a thickness of the single crystal silicon wafer is routinely set to about 0.725 mm.
In a case where the silicon wafer is used as the dummy wafer in the above film forming process, various films adhered and formed on the wafer are removed by means of chemical solutions or mechanical methods such as polishing or the like, thereby to regenerate the silicon wafer, and then the regenerated silicon wafer is repeatedly reused.
Further, in recent years, as disclosed in Japanese Patent Laid-Open Publication No. 10(1998)-270433 or No. 11(1999)-102847, a dummy wafer using a glassy carbon plate had been developed. However, when the glassy carbon plate is used as a plate member, it is required to form a sintered body of the glassy carbon, and then, required to perform a grinding work for the sintered body so as to obtain a predetermined size and shape. Furthermore, in order to grind the plate (sintered body) composed of the glassy carbon, it is necessarily required to use a high-priced diamond-grinding machine, thus has been a factor of increasing a manufacturing cost of the dummy wafer.
Furthermore, there exist a probe pin (probe needle) and a contact for socket (contactor) as concrete examples of the member for constituting the semiconductor-manufacturing device. These probe pin and the contact for socket are used as members for constituting an inspection device for inspecting whether the semiconductor devices such as integrated circuit (LSI) or the like are well-behaved or not.
For example, as shown in FIG. 4A and also disclosed in Japanese Patent Laid-Open Publication No. 10(1998)-221366, the probe pin 30 is composed of, for example, Re—W alloy wire, and is formed by sharpening a top portion of the wire. The top portion of the probe pin 30 is abut against Al electrode pad 38 formed on a substrate 37 thereby to enable the probe pin 30 to be electrically connected to a test circuit, whereby electrical characteristics of the electronic devices or semiconductor packages are measured.
However, the above conventional probe pin composed of Re—W alloy wire is insufficient in wear resistance and strength. Therefore, when the contact operation to contact the electrode portion is repeated, there arise a problem such that the top portion of the probe pin easily wear and/or deform thereby to lower an accuracy in shape of the probe pin. In addition, metal components of the electrode and solder are liable to adhere to the top portion of the probe pin, so that a contact resistance (junction resistance) at the probe pin is disadvantageously varied and increased. As a result, there may be posed problems such that the inspection accuracy is liable to lower and the life (duration time) of the probe pin is shortened.
On the other hand, in a case where the aforementioned pure diamond film (DLC film: Diamond-Like Carbon film) is applied to members for machine parts or tools to be used under severe conditions, when the thickness of the pure diamond film is set to be large, a stress caused in the diamond film becomes extremely large, so that there arise a fatal defect of causing a flaking exfoliation (peeling in a flake-shape) in a short period of time.
The film peeled in a flake-shape is then finely pulverized to generate powder. When the powder adheres to the semiconductor products, the powder has become a strong factor for lowering a production yield of the semiconductor products.
Further, at a member to which energy beams such as plasma, ion beam or electron shower was irradiated in a wafer-processing unit to be used in a process of manufacturing the semiconductor device, constituent element of the member was separated by the energy beams and mixed into the wafer, so that there were many cases where the mixed element exerted a bad influence onto the wafer in view of purity thereof. In addition, there was also posed a problem the member per se was liable to be easily deteriorated thereby to lower a durability of the semiconductor device.
Furthermore, in processes represented by ion-injecting treatment, dry-etching treatment, sputtering treatment for processing the wafer or liquid crystal display (LCD) substrate, a transferring unit for transfer the wafer and the glass substrate, and a wafer cassette for holding a number of wafers are essential units. In these unit and cassette, there necessarily exists a sliding portion at which semiconductor products such as wafer or the like slide to each other.
However, as the integration degree of the semiconductor integrated circuit and a pixel number of the liquid crystal display device are increased, an influence of the particles (fine grains) that are generated by rubbing and sliding of the semiconductor products at the sliding portion of the semiconductor equipment has become remarkable. Therefore, for the purpose of improving the production yield of the semiconductor products, a reduction of the particle amount has become a burning technical problem in these days.
On the other hand, in a case where glassy carbon is used as the semiconductor manufacturing apparatus member as described hereinbefore, the following drawbacks are disadvantageously posed. That is, the glassy carbon has a poor workability, and is very expensive material. In addition, it is quite difficult for the glassy carbon to provide a member having a large thickness, so that the member cannot be applied to a large-sized chamber of which size has been further increased in response to a scale-up in area of the wafer. Therefore, there has been posed a problem that it is extremely difficult to provide the member capable of being used in a stable state under a high vacuum condition.
On the other hand, according to the member formed with a film composed of only pure amorphous carbon (hereinafter referred to as “pure amorphous carbon film”) as mentioned hereinbefore, although the member is excellent in low-friction coefficient and wear resistance, if the film thickness is increased so as to secure a sufficient durability in view of the severe using conditions such as the operating environment for the machine parts or tools, an internal stress of the coated film is greatly increased, whereby the flaking exfoliation is liable to occur. Therefore, there is also posed a problem that an applicable usage of the member is disadvantageously limited to a narrow range.
Furthermore, in a case where a film formation is conducted by using a silicon-wafer as a dummy wafer, when the dummy wafer is immersed into a strong acid solution for the purpose of removing various films adhered to the silicon wafer thereby to regenerate the used wafer, the silicon wafer per se is eluted into the acid solution and then remarkably thinned in a short period of time. In this situation, the thickness of the silicon wafer becomes smaller than 0.6 mm which is usually prescribed as a controlled lower limit, so that it becomes impossible to reuse or recycle the silicon wafer.
In addition, when the silicon wafer was thinned by being immersed into the acid solution, there was also a case where the wafer caused a breakage due to insufficient strength. Further, in a case where the film-removal operation was performed by a mechanical method such as polishing or the like, the silicon wafer together with the film were simultaneously polished. Therefore, the thickness of the silicon wafer was thinned to a level below the controlled lower limit, so that there existed a disadvantage such that it became impossible to repeatedly reuse the silicon wafer. In also a case of chemical polishing method such as chemical-mechano-polishing (CMP) method using chemicals, the same problems as described above had been raised.
Further, in a case where the dummy wafer is used in a wafer processing unit to which energy beams such as plasma, ion beam, electron shower or the like are irradiated as in a process of manufacturing the semiconductor device, it is not possible to use a material of which constituent element is separated by the energy beams such as plasma or the like and is mixed to the wafer so as to exert a bad influence onto the wafer in view of purity thereof.
As described hereinbefore, as the integration degree of the semiconductor integrated circuit and a pixel number of the liquid crystal display device are increased, an influence of the particles (fine grains) that are generated by rubbing and sliding of the semiconductor products at the sliding portion of the semiconductor equipment has become remarkable. Therefore, as a material for constituting the dummy wafer, it is not possible to use a material, which generates the particles by contacting to a transfer part.
As explained above, there has been also posed a requirement for the material constituting the dummy wafer so as not to exert the bad influence on a quality of the wafer, so that a suitable material having both chemical resistance and durability has been sought in these days.
On the other hand, there is also a case where a dummy wafer composed of SiC and comprising a film formed by CVD method or a dummy wafer composed of glassy carbon are used in place of the conventional dummy wafer composed of silicon. However, Sic and the glassy carbon are poor in workability and expensive materials. In addition, in a case where these materials are used, it is difficult to obtain a wafer having a large diameter of 12-inch class and a large surface area.
For example, when a dummy wafer composed of a material different from silicon was used, the following problems were posed. That is, it was impossible to perform a detecting operation for detecting a position of the dummy wafer by means of a position sensor, the detecting operation being required in quality control step and an evaluation process. In addition, there existed a problem such that it was extremely difficult to provide a dummy wafer, which can be used in a stable state under a vacuum condition.
On the other hand, according to the member in which a pure amorphous carbon film composed of only pure amorphous carbon is formed on a surface of a wafer base material, although the member (dummy wafer) was excellent in low-friction coefficient and wear resistance, if the film thickness was increased so as to secure sufficient chemical resistance and durability in view of the severe operating conditions, an internal stress of the coated film was greatly increased, whereby the flaking exfoliation was liable to occur. Therefore, there was also posed a problem that an applicable usage of the member was disadvantageously limited to a narrow range.